Short answer is yes, that is entirely allowed. Great information has already been provided in Tom's answer and Adam's answer.

If you are already certain that you'll be purchasing a Craft Client account, then you won't have to do anything special to get the site working locally. As long as the same license key remains in your site, any purchased upgrades will remain available to you... regardless of whether the site is running locally or on a server!

Not sure how familiar you are with this, but you may want to learn more about multi-environment configurations in Craft. It's incredibly easy to move your website between environments without losing any rights or privileges.

You can run your site locally without any warnings as long as you're using a dev-sounding domain. Read this article... All of the answers you're looking for should be in here: